![Mark Rutland](/assets/img/avatar_default.png)
For a while now it's been possible to use EXPORT_SYMBOL() in assembly files, which allows us to place exports immediately after assembly functions, as we do for C functions. As a step towards removing arm64ksyms.c, let's move the string routine exports to the assembly files the functions are defined in. Routines which should only be exported for !KASAN builds are exported using the EXPORT_SYMBOL_NOKASAN() helper. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
236 lines
6.6 KiB
ArmAsm
236 lines
6.6 KiB
ArmAsm
/*
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* Copyright (C) 2013 ARM Ltd.
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* Copyright (C) 2013 Linaro.
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*
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* This code is based on glibc cortex strings work originally authored by Linaro
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* and re-licensed under GPLv2 for the Linux kernel. The original code can
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* be found @
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*
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* http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
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* files/head:/src/aarch64/
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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/*
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* compare two strings
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*
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* Parameters:
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* x0 - const string 1 pointer
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* x1 - const string 2 pointer
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* Returns:
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* x0 - an integer less than, equal to, or greater than zero
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* if s1 is found, respectively, to be less than, to match,
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* or be greater than s2.
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*/
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#define REP8_01 0x0101010101010101
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#define REP8_7f 0x7f7f7f7f7f7f7f7f
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#define REP8_80 0x8080808080808080
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/* Parameters and result. */
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src1 .req x0
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src2 .req x1
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result .req x0
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/* Internal variables. */
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data1 .req x2
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data1w .req w2
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data2 .req x3
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data2w .req w3
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has_nul .req x4
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diff .req x5
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syndrome .req x6
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tmp1 .req x7
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tmp2 .req x8
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tmp3 .req x9
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zeroones .req x10
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pos .req x11
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WEAK(strcmp)
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eor tmp1, src1, src2
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mov zeroones, #REP8_01
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tst tmp1, #7
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b.ne .Lmisaligned8
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ands tmp1, src1, #7
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b.ne .Lmutual_align
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/*
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* NUL detection works on the principle that (X - 1) & (~X) & 0x80
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* (=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and
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* can be done in parallel across the entire word.
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*/
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.Lloop_aligned:
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ldr data1, [src1], #8
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ldr data2, [src2], #8
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.Lstart_realigned:
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sub tmp1, data1, zeroones
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orr tmp2, data1, #REP8_7f
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eor diff, data1, data2 /* Non-zero if differences found. */
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bic has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
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orr syndrome, diff, has_nul
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cbz syndrome, .Lloop_aligned
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b .Lcal_cmpresult
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.Lmutual_align:
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/*
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* Sources are mutually aligned, but are not currently at an
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* alignment boundary. Round down the addresses and then mask off
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* the bytes that preceed the start point.
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*/
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bic src1, src1, #7
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bic src2, src2, #7
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lsl tmp1, tmp1, #3 /* Bytes beyond alignment -> bits. */
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ldr data1, [src1], #8
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neg tmp1, tmp1 /* Bits to alignment -64. */
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ldr data2, [src2], #8
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mov tmp2, #~0
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/* Big-endian. Early bytes are at MSB. */
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CPU_BE( lsl tmp2, tmp2, tmp1 ) /* Shift (tmp1 & 63). */
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/* Little-endian. Early bytes are at LSB. */
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CPU_LE( lsr tmp2, tmp2, tmp1 ) /* Shift (tmp1 & 63). */
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orr data1, data1, tmp2
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orr data2, data2, tmp2
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b .Lstart_realigned
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.Lmisaligned8:
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/*
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* Get the align offset length to compare per byte first.
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* After this process, one string's address will be aligned.
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*/
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and tmp1, src1, #7
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neg tmp1, tmp1
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add tmp1, tmp1, #8
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and tmp2, src2, #7
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neg tmp2, tmp2
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add tmp2, tmp2, #8
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subs tmp3, tmp1, tmp2
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csel pos, tmp1, tmp2, hi /*Choose the maximum. */
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.Ltinycmp:
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ldrb data1w, [src1], #1
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ldrb data2w, [src2], #1
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subs pos, pos, #1
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ccmp data1w, #1, #0, ne /* NZCV = 0b0000. */
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ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
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b.eq .Ltinycmp
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cbnz pos, 1f /*find the null or unequal...*/
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cmp data1w, #1
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ccmp data1w, data2w, #0, cs
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b.eq .Lstart_align /*the last bytes are equal....*/
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1:
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sub result, data1, data2
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ret
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.Lstart_align:
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ands xzr, src1, #7
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b.eq .Lrecal_offset
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/*process more leading bytes to make str1 aligned...*/
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add src1, src1, tmp3
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add src2, src2, tmp3
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/*load 8 bytes from aligned str1 and non-aligned str2..*/
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ldr data1, [src1], #8
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ldr data2, [src2], #8
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sub tmp1, data1, zeroones
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orr tmp2, data1, #REP8_7f
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bic has_nul, tmp1, tmp2
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eor diff, data1, data2 /* Non-zero if differences found. */
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orr syndrome, diff, has_nul
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cbnz syndrome, .Lcal_cmpresult
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/*How far is the current str2 from the alignment boundary...*/
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and tmp3, tmp3, #7
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.Lrecal_offset:
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neg pos, tmp3
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.Lloopcmp_proc:
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/*
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* Divide the eight bytes into two parts. First,backwards the src2
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* to an alignment boundary,load eight bytes from the SRC2 alignment
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* boundary,then compare with the relative bytes from SRC1.
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* If all 8 bytes are equal,then start the second part's comparison.
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* Otherwise finish the comparison.
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* This special handle can garantee all the accesses are in the
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* thread/task space in avoid to overrange access.
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*/
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ldr data1, [src1,pos]
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ldr data2, [src2,pos]
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sub tmp1, data1, zeroones
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orr tmp2, data1, #REP8_7f
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bic has_nul, tmp1, tmp2
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eor diff, data1, data2 /* Non-zero if differences found. */
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orr syndrome, diff, has_nul
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cbnz syndrome, .Lcal_cmpresult
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/*The second part process*/
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ldr data1, [src1], #8
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ldr data2, [src2], #8
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sub tmp1, data1, zeroones
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orr tmp2, data1, #REP8_7f
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bic has_nul, tmp1, tmp2
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eor diff, data1, data2 /* Non-zero if differences found. */
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orr syndrome, diff, has_nul
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cbz syndrome, .Lloopcmp_proc
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.Lcal_cmpresult:
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/*
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* reversed the byte-order as big-endian,then CLZ can find the most
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* significant zero bits.
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*/
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CPU_LE( rev syndrome, syndrome )
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CPU_LE( rev data1, data1 )
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CPU_LE( rev data2, data2 )
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/*
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* For big-endian we cannot use the trick with the syndrome value
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* as carry-propagation can corrupt the upper bits if the trailing
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* bytes in the string contain 0x01.
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* However, if there is no NUL byte in the dword, we can generate
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* the result directly. We ca not just subtract the bytes as the
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* MSB might be significant.
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*/
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CPU_BE( cbnz has_nul, 1f )
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CPU_BE( cmp data1, data2 )
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CPU_BE( cset result, ne )
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CPU_BE( cneg result, result, lo )
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CPU_BE( ret )
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CPU_BE( 1: )
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/*Re-compute the NUL-byte detection, using a byte-reversed value. */
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CPU_BE( rev tmp3, data1 )
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CPU_BE( sub tmp1, tmp3, zeroones )
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CPU_BE( orr tmp2, tmp3, #REP8_7f )
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CPU_BE( bic has_nul, tmp1, tmp2 )
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CPU_BE( rev has_nul, has_nul )
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CPU_BE( orr syndrome, diff, has_nul )
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clz pos, syndrome
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/*
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* The MS-non-zero bit of the syndrome marks either the first bit
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* that is different, or the top bit of the first zero byte.
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* Shifting left now will bring the critical information into the
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* top bits.
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*/
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lsl data1, data1, pos
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lsl data2, data2, pos
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/*
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* But we need to zero-extend (char is unsigned) the value and then
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* perform a signed 32-bit subtraction.
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*/
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lsr data1, data1, #56
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sub result, data1, data2, lsr #56
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ret
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ENDPIPROC(strcmp)
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EXPORT_SYMBOL_NOKASAN(strcmp)
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